1. Field of the Invention
The present invention relates to a microfluidic device using a microfluidic chip.
2. Description of the Related Art
Recently, micro electro mechanical systems (MEMS) have been interested in the fields of, for example, biology, environmental analysis, and chemical synthesis. One of the fields with MEMS applied may be micro total analysis systems (μTAS). μTAS collectively perform chemical synthesis and chemical analysis on a microchip. A microfluidic chip is used as the microchip. The microfluidic chip is formed such that a microchannel is formed in a substrate made of a semiconductor, glass, ceramic, synthetic resin, or the like. For example, an analyte, a reagent, and/or liquid or powder (hereinafter, referred to as fluid) which is a material for the chemical synthesis, flows through the channel, and the chemical analysis or chemical synthesis is performed in the microfluidic chip. With the use of the microfluidic chip, the chemical analysis or chemical synthesis using fluid with a very small amount is available, and a feature of a high reaction rate is obtained. Thus, development of the microfluidic device using the microfluidic chip is desired.
For the actual use of the microfluidic chip, a unit of measuring and acquiring a sample for analysis by a given amount is necessary. Owing to this, a valve is provided in the channel of the microfluidic chip. The microfluidic chip having the valve may be one having a diaphragm valve or one that deforms a channel to control the flow of fluid in the channel.
U.S. Pat. No. 5,932,799 (hereinafter, referred to as the '799 document) discloses in the specification a microfluidic chip having a diaphragm valve. FIGS. 10A and 10B are cross-sectional views schematically showing the microfluidic chip described in the '799 document. A microfluidic chip 101 includes a substrate 108 in which channels 102a and 102b are formed. Referring to FIG. 10A, a diaphragm 103 is provided to close the upstream channel 102a and the downstream channel 102b. The diaphragm 103 is formed of a deformable member. A driving unit 104 is connected so as to deform the diaphragm 103. By deforming the diaphragm 103 using the driving unit 104, the state is switched between a state in which the upstream channel 102a and the downstream channel 102b are decoupled (see FIG. 10A) and a state in which the channels 102a and 102b are coupled (see FIG. 10B).
U.S. Pat. No. 6,408,878 (hereinafter, referred to as the '878 document) discloses in the specification a microfluidic chip that deforms a channel to control the flow of fluid. FIGS. 11A and 11B are cross-sectional views schematically showing the microfluidic chip described in the '878 document. A microfluidic chip 111 includes a substrate 118 in which a channel 112 is formed. Fluid such as a reagent or an analyte flows through the channel 112. The substrate 118 also has a valve driving channel 114 so as to three-dimensionally intersect with the channel 112. At least a portion in which the channel 112 three-dimensionally intersects with the valve driving channel 114 is made of a soft material such as, for example, poly-dimethyl siloxane (PDMS) 113. FIG. 11A illustrates the microfluidic chip 111 in a state in which the upstream side and the downstream side of the channel 112 are coupled. To decouple the upstream side from the downstream side of the channel 112, compressed air is applied to the valve driving channel 114. Accordingly, the pressure in the valve driving channel 114 increases, and the PDMS 113 is deformed. The deformed PDMS 113 presses the channel 112, thereby blocking the flow in the channel 112.
As described above, with the microfluidic chip described in the specification of the '799 document or the '878 document, a sample, which is necessary for analysis and which flows in the channel, can be measured and acquired by a given amount.
However, in the microfluidic chip described in the specification of the '799 document, the driving unit has to be provided to deform the diaphragm, resulting in a complicated structure. Thus, the microfluidic chip becomes large and expensive.
Also, in the microfluidic chip described in the specification of the '878 document, the valve driving channel has to be largely deformed, thereby reducing durability. In addition, the soft material such as PDMS causes the liquid or gas, in particular, a vaporized material to leak, and the leakage produces contamination.